Browsing by Author "Vale, Maria"
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- Evidence of long-term changes in the distribution of key intertidal speciesPublication . Vale, Maria; Neto, Ana I.; Martins, Gustavo M.; Hawkins, Stephen J.Globally, changes are occurring in the biogeochemistry and ecology of the oceans, which may influence the physiology, phenology, and species distribution. Biological communities are reacting to climate change through changes in the abundance and phenology of the organisms and through the poleward shift in species distribution. Rocky shores are relatively simple ecosystems, which makes them an excellent model system for the understanding of the consequences of climate change. This study aims to examine the evidence of long-term changes on the distribution of key intertidal species in the Azores. Grey literature and unpublished data collected in the late 1980’s by Stephen J. Hawkins and his colleagues in the island of São Miguel (Azores) was compared to data collected in 2012. Whilst most taxa sampled in 1988 were still present during 2012, there were changes in species distribution. In general, there was an overall decrease in the abundance of organisms that was more pronounced on the sheltered area. In addition, there was generally a shift upwards of the vertical distribution of taxa that was more pronounced on the exposed area. These changes are temptatively interpreted as a consequence of increased temperatures and wave action (both predicted by climate change scenarios). This study also suggests that there may be interactive effects between environmental processes affecting species distributions. In addition, there was evidence that processes operating at large temporal scales may indirectly influence the distribution of species via changes in the abundance of their competitors.
- Temporal variation in reproductive phenology of Patella spp.: past and present.Publication . Vale, Maria; Ribeiro, Pedro; Golbold, J.; Neto, Ana I.; Martins, Gustavo M.; Hawkins, Stephen J.Global changes occurring in the biogeochemistry o f the oceans may influence the ecology of the biota. There is evidence that species are reacting to changes in climate through variations in the abundance and phenology with many species showing a poleward shift in their distributional range. The rocky intertidal is a relatively simple ecosystem but highly susceptible to anthropogenic activities and is thus an excellent model system for the understanding of the consequences of change in climate. This study presents a preliminary analysis of the changes in gonad phenology of Patella aspera over time. Patella aspera is being collected in various locations of the São Miguel Island (Azores) and their gonad development assessed visually using a trained observer. These data are then compared to unpublished data on gonad development collected in the period of 1985-1987 through a chi-square test of independence. Overall, in contrast to the period of 1985-87, there was a much lower number of individuals reaching maturity (gonad development stages IV and V) in 2012-2013 and there was no clear peak in spawning. In addition, the resting period appears to be starting in june, one month delayed compared to data from 1985-87. These variations are important and may affect the population dynamics of the species.